This invention relates to toothbrushes, particularly toothbrushes for use by hand action and having a flexibility-modifying feature in their handle.
Toothbrushes having flexibility-modifying features in their handle are known, for example U.S. Pat. No. 5,054,154 discloses the possibility of a toothbrush having a hinge between its grip handle and its neck, i.e. that part of the toothbrush between the handle and the head. Generally however, the flexibility modifying features of known toothbrushes have been unable to focus the flexibility of the toothbrush at a precise point in the toothbrush structure, so that as a consequence the flexible bending of the toothbrush occurs over a vaguely defined zone. Also precise xe2x80x9ctuningxe2x80x9d of the flexibility of the toothbrush can be difficult with known constructions.
An object of this invention is to overcome the above-mentioned problems of known toothbrushes and to provide a toothbrush in which flexibility can be focused at a precisely defined location and can be easily tuned independently of selection of particular construction materials for the toothbrush.
According to this invention a toothbrush has a head and a grip handle, with a neck in between the head and grip handle, all disposed along a longitudinal toothbrush axis, bristles projecting from the head in a direction generally perpendicular to the toothbrush axis, having a hinge located between its head and its handle, the hinge being provided by a first hinge part extending from the head end of the toothbrush toward the handle end, and a second hinge part extending from the handle end toward the head end, the said first and second hinge parts being arranged in a longitudinally overlapping side by side relationship on opposite sides of a plane parallel to the longitudinal axis and to the bristle direction, the overlapping parts being able to rotate relative to each other through a restricted angle about an axis generally perpendicular to the longitudinal axis and to the bristle direction, the two parts being linked by a torsion element between them.
The hinge may be located at any part of the toothbrush between the head and the handle but is preferably located either between the handle and the neck or between the neck and the head. In this description the head is defined as that part of the toothbrush which bears the bristles, the handle is defined as that part of the toothbrush which is held by the hand during use, and the neck is defined as that part of the toothbrush between the head and handle. Often a toothbrush narrows over the neck region between the handle and head.
The direction of the said relative rotation is suitably from an initial unstressed rest position to a position where the toothbrush head is displaced from its rest position in the bristle tipxe2x80x94toothbrush head direction, and the torsion element is suitably an element which is capable of providing torsional force to return the head in the opposite direction toward, ideally into, the rest position. The said displacement is caused by pressure applied to the tips of the bristles by the action of the user brushing his/her teeth and consequently applying pressure thereto.
In one embodiment the toothbrush has a single first hinge part extending from the head end of the toothbrush toward the handle end, and a single second hinge part extending from the handle end toward the head end, the first and second hinge parts being respectively on either side of a plane parallel to and which includes the longitudinal axis.
In another embodiment the toothbrush has at least two respectively first or second hinge parts extending respectively either from the head end of the toothbrush toward the handle end, or from the handle end of the toothbrush toward the head end, and respectively either a second hinge part extending from the handle end toward the head end and between two of the said at least two first hinge parts, or a first hinge part extending from the head end toward the handle end between two of the said at least two second hinge parts.
The toothbrush of the invention may be provided as a separate head end and handle end. In one embodiment these may be connected only by the torsion element. Alternatively the toothbrush of the invention may have an integral head end and handle end, with at least part of the torsional element formed integrally between and linking them.
For example a separate head end and handle end may be constructed having respective connecting parts which co-operate together to retain the head end and handle end together. For example such connecting parts may co-operate by a snap fit co-operation, i.e. where one or both of the connecting parts are resilient and the action of bringing the connection parts together forces a ramp surface on one part over and beyond a ramp surface on the other part, so that to disconnect the connecting parts again requires resilience to be overcome. If the head end and handle end are made of resilient plastics materials the resilience of such plastics materials can be used to provide such a resilient snap-fit connection.
There may be an axle defining the axis of relative rotation. This axle may pass through a bearing hole, or fit into a bearing socket, respectively through or in at least the first or second hinge part. For example the bearing hole may be in the form of an axle hole passing completely through the respective first and/or second part. For example the bearing socket may be in the form of a concavity, not passing all the way through the respective first or second part, and in which sits the stub end of the axle. Such an axle may be separate to or integral with the first or second hinge part, and the said relative rotation through a restricted angle may be about this axis. Alternately the parts may be linked by a torsion element, which may be integral with the first and/or second hinge parts.
When the toothbrush is of the above described separate head end and handle end construction the head end and handle end may be made of different constructional materials or differently colored materials to for example visually emphasis its construction.
The torsion element is an element that applies torsion against and to restrict the relative rotation of the parts, so that the two parts can only rotate through a restricted angle relative to each other, and this rotation generates a resilient torsional effect tending to return the toothbrush toward the original rest configuration of the first and second parts. The torsion element thereby imparts flexibility into the handle of the toothbrush, helping to reduce the possibility of excessive toothbrushing pressure.
One type of torsion element comprises a torsion element made of resilient material, for example made of the plastics material of which the head end and handle end of the toothbrush are made, connected to the head end and handle end, e.g. integrally connected, and located between them. Such a torsion element may comprise a laterally extending, i.e. perpendicular to the direction of the toothbrush longitudinal axis, torsion bar. This torsion bar may be of any suitable cross section, e.g. of non-circular cross section about the axis of relative rotation of the head end and handle end, made of a resilient material, which may be integrally made of the plastics material of the toothbrush head end or handle end. Such a torsion bar may extend completely or partially across the toothbrush width between the said first and second hinge parts. Such a torsion bar may link, e.g. integrally link, the first and second hinge parts. When one of respectively the said head or handle ends is provided with such a torsion bar the other end may be provided with an axle socket into and preferably through which the torsion bar extends, the axle socket being of cross section similar to the torsion bar.
Suitably such a torsion bar and axle socket may also comprise the connecting parts referred to above, for example the torsion bar may snap-fit into the axle socket. Alternatively the torsion bar may integrally link the first and second parts as mentioned above.
Another type of torsion element comprises an elastomeric material, bonded to the head end and/or handle end, e.g. to one or both of the said first and second hinge parts, and located between them. Methods of binding elastomeric and plastic materials in toothbrushes are well known in the art of toothbrush manufacture. For example the plastic and elastomeric parts may be fused together, e.g. as disclosed in WO 98/27847. Such an elastomeric material may prevent unlimited free rotation of the parts relative to each other and may cause the parts to rotate relatively only through the said restricted angle. Such an elastomeric material may be in the form of an infilling between the head and handle end, e.g. between the first and second hinge parts. Such an infilling may be in the form of a layer, e.g. sandwiched laterally between the said overlapping parts. In this construction the natural elasticity of the elastomeric material may serve to generate the required torsional force when the first and second hinge parts rotate relative to each other through their restricted angle.
Additionally or alternately the elastomeric material may be in the form of a torsion bar extending between the head end and handle end, e.g. between the first and second hinge parts, and may be aligned with the axis about which the said relative rotation through a restricted angle takes place. Such a torsion bar twists as the said parts rotate relative to each other, and a torsion force is thereby generated. Such an elastomeric torsion bar may be bonded to the plastic material of the said first and second parts.
Such an infilling may comprise a composite structure of elastomer and the plastic material of the toothbrush. In such a structure the plastic material may be in the form of structures extending within the infilling from the surface of the head end and handle end, e.g. the first and second hinge parts, which resist the said relative rotation, so as to make the infilling less flexible than it would be without such structures. For example such a composite structure may comprise a mass of elastomeric material, and embedded within this mass there may be plastic material parts linked with, e.g. integrally made with, the first and/or second parts such that when the first and second parts move relative to each other e.g. through the restricted angle the plastic material parts attempt to move within the elastomer mass and thereby experience a torsional force resulting from the natural elasticity of the elastomer material mass.
Such a construction can allow flexing of the toothbrush preferentially in the plane that includes the longitudinal axis and the bristle direction, and can also provide damping of the flexibility. In this way flexibility in other directions such as widthwise can be limited. The elastomeric material in this construction can consequently function as a fully floating bearing.
Another type of torsion element comprises a thin link of a resilient material, preferably integral with the plastic material of the first and second hinge parts and made of the plastic material of the toothbrush, between the head end and handle end, e.g. between the first and second hinge parts such that the relative rotation of the said parts as described above about the axis applies a twisting force to the link, which thereby can, if it is of suitable dimensions, generate a torsion force against the said rotation.
For example such a link may comprise a spiral or helical structure of the plastic material linking the head end and handle end, e.g. between and linking the first and second hinge parts. Such a spiral or helical structure may be integrally made with the plastic material of the head and handle end, e.g. of the first and second hinge parts. The centre of the spiral structure or the axis of the helical structure may comprise the axis about which the said relative rotation takes place. There may be an axle at the centre of the spiral or helix, and the helical or spiral structure(s) may be linked to his axle. Such a spiral structure may comprise a plurality of arms radiating in a spiral curve from a centre of the spiral. Such a helical structure may comprise one or more coils of a helix surrounding a central helix axis. For example if there is a single first or second hinge part located laterally between respectively two second or first hinge parts there may be two such spiral or helical structures. For example the first and/or second hinge part may have an opening therein, with the centre of the spiral structure located at or near the centre of the opening, and the outer ends of the spiral arms may be linked to the inner surface of the opening.
When such a spiral or helical structure is present, the said relative rotation between the first and second hinge parts may wind the spiral or helix up, and thereby create a torsion force in the opposite twist direction. In one form of such a construction a spiral structure may comprise a central axle defining the axis of relative rotation of the first and second hinge parts, and linked, e.g. integrally made with the first or second hinge part, from which radiate one or preferably more spiral arms, the spiral arm(s) being linked, preferably integrally, respectively with the second or first hinge part. In one form of such a construction a helical structure may comprise a central axle defining the axis of relative rotation of the first and second hinge parts, and linked, e.g. integrally made with the first or second hinge part, from which radiate one or more helical arms, the helical arm(s) being linked, preferably integrally, respectively with the second or first hinge part.
The link may alternatively be made so thin that it effectively makes no practical contribution to the flexibility of the link, and can be provided primarily to allow the plastic parts of the toothbrush to be molded integrally of plastic material, e.g. the link may be formed by residual plastic material in an injection molding channel, with the torsion element comprising an elastomeric material between the first and second hinge parts. Such a thin link can be made so thin that it can flex completely freely or even snap or shear when the toothbrush is used, e.g. for the first time, so that the elastomeric material acts as the torsion element, because when such a link is used in a toothbrush of the invention, an elastomeric material as described above is also present between the parts.
Another type of torsion member is provided by a construction in which the head end and handle end are provided with respective torsion parts, at least one of which is resilient, and such that when the head end and handle end rotate relative to each other the respective torsion parts bear upon each other, e.g. as a result of the relative movement of one torsion part circumferentially relative to another, and the resilience generates a torsional force. Suitably the resilience of the said torsion parts is provided by at least one of them comprising a resilient elastomeric material.
For example one or more of the said torsion parts may comprise a first part extending radially from the axis of relative rotation of the head end and handle end, and the other part may comprise a second part located upon the arc followed by the first part during the relative rotation, such that the first and second parts bear upon each other during the relative rotation. One or both of such first and second parts may comprise a resilient elastomeric material.
For example alternatively two of respectively the first and second torsion parts may be located upon the arc followed by the first or second torsion part during the relative rotation, such that the first and second parts bear upon each other during the relative rotation. One or both of such first and second parts may comprise a resilient elastomeric material.
The toothbrush of the invention may also include co-operating end-stop means to encourage or cause the said parts to rotate relative to each other only through a restricted angle, e.g. structures which abut against each other at the limits of the restricted angle to thereby prevent further relative rotation. Such structures may for example project from facing surfaces of the overlapping parts, e.g. the surfaces of the first and second hinge parts, and may be respectively integral with such parts. When the link between the head end and handle end, e.g. between and linking the first and second hinge parts comprises the abovementioned spiral or helical structure of the plastic material, then such a structure may also function as an end-stop means by virtue of the spiral or helix becoming wound up and unable to rotate any further in a particular rotation direction.
By means of the above described construction of the toothbrush of the invention the flexibility of the toothbrush may be made independent of the plastic material of the toothbrush end, and for example can be determined by the composition, amount or shape of the elastomeric material. Moreover the flexibility of the handle can be determined by the position and construction of the hinge, so as to focus flexibility at a precise point in the toothbrush.